Any idea why it won't allow me to change the finish date?

• Because as the software said, "Remain Finish Date cannot be earlier than Remain Start Date."

I suspect the Remaining Start Date is being delayed further than DD. But why Remain Start Date is delayed even when all predecessors have finished?

It might be that there is still an out-of-sequence link that is still active if the link have a lag value that have not elapsed completely. In such case Remaining Start will be delayed to the date where active lag will have completely elapsed.

Unfortunately most/none CPM software disclose Remaining Lag, not to mention Relationship Slack.

http://www.ronwinterconsulting.com/Making_CPM_Transparent.pdf

In-Progress Lag Report and Value: Remaining Lag should be displayed just as remaining duration is shown and editable. The CPM feature of Remaining Duration was added so that Schedulers could monitor and change this calculated duration result. Lags are to relationships what durations are to activities. Why should Remaining Lag calculations be discarded by the software instead of
saved and displayed? Why should we be unable to indicate that actual remaining lag is only 2 days instead of the calculated 4 days? Part of the reason CPM Schedules are so hard to understand is that fact that not all of the data used is displayed.

http://scheduleanalyzer.com/sa_long_theory.htm

The term “slack” as it concerns a CPM relationship is the amount of ‘unused’ time difference between the predecessor and the successor activities. This slack value has nothing to do with the float values or either of the two activities that it relates. It merely indicates how close each predecessor is to becoming the driving relationship for the successor activity.

Spider project have the option to setup out-of-sequence to ignore preceding links of activities finished but I still prefer to fix logic. No single out-of-sequence rule will correctly fix all possible occurrences.

Good luck,

Rafael